I am building a circuit having multiple loads. Each load has different specs needing different volts and amps, each load is being wired parallel,all from one power supply.

When I calculate resistors for each load, the equation calls for the supply volts, the load volts and amps. It never ask for the amps being supplied.

Question: Does the amperage of different power supplies having the same voltage have any effect on choosing the correct size resistor.

Example:

two different power packs:

power supply pack #1 specs are: 12V, 500mA

power supply pack #2 specs are: 12V, 3A

I think I am suppose to add up the max amps on the entire circuit to know the correct amperage for the power supply pack. But I don't get the amps part completely. If one load needs a 1/4 watt 1000 ohm resistor and another load on the same circuit calls for 2 watt 150 ohm resistor then won't a large amount of supply amps harm the small resistor vs safe on the larger resistor?